Aquifer depletion

Due to agricultural pumping and resulting depletion of the Ogallala Aquifer, the White River no longer maintains a spring-fed base flow and, today, Silver Falls is often dry and overgrown by vegetation. (By Leaflet, via Wikimedia Commons)

Scores of countries are overpumping aquifers as they struggle to satisfy their growing water needs, including each of the big three grain producers—China, India, and the United States. These three, along with a number of other countries where water tables are falling, are home to more than half the world’s people. (See Table at end of article.)

There are two types of aquifers: replenishable and nonreplenishable (or fossil) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge.

For fossil aquifers—such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer—depletion brings pumping to an end. Farmers who lose their irrigation water have the option of returning to lower-yield dryland farming if rainfall permits. In more arid regions, however, such as in the southwestern United States or the Middle East, the loss of irrigation water means the end of agriculture.

Falling water tables are already adversely affecting harvests in some countries, including China, the world’s largest grain producer. A groundwater survey released in Beijing in August 2001 revealed that the water table under the North China Plain, which produces over half of that country’s wheat and a third of its corn, is falling faster than earlier reported. Overpumping has largely depleted the shallow aquifer, forcing well drillers to turn to the region’s deep fossil aquifer, which is not replenishable.

The survey, conducted by the Geological Environmental Monitoring Institute (GEMI) in Beijing, reported that under Hebei Province in the heart of the North China Plain, the average level of the deep aquifer was dropping nearly 3 meters (10 feet) per year. Around some cities in the province, it was falling twice as fast. He Qingcheng, head of the GEMI groundwater monitoring team, notes that as the deep aquifer is depleted, the region is losing its last water reserve—its only safety cushion.

He Qingcheng's concerns are mirrored in a World Bank report: “Anecdotal evidence suggests that deep wells [drilled] around Beijing now have to reach 1,000 meters [more than half a mile] to tap fresh water, adding dramatically to the cost of supply.” In unusually strong language for a Bank report, it foresees “catastrophic consequences for future generations” unless water use and supply can quickly be brought back into balance.

The U.S. embassy in Beijing reports that wheat farmers in some areas are now pumping from a depth of 300 meters, or nearly 1,000 feet. Pumping water from this far down raises pumping costs so high that farmers are often forced to abandon irrigation and return to less productive dryland farming.

Falling water tables, the conversion of cropland to nonfarm uses, and the loss of farm labor in provinces that are rapidly industrializing are combining to shrink China’s grain harvest. The wheat crop, grown mostly in semiarid northern China, is particularly vulnerable to water shortages. After peaking at 123 million tons in 1997, the harvest has fallen in five of the last eight years, coming in at 95 million tons in 2005, a drop of 23 percent.

The U.S. embassy also reports that the recent decline in rice production is partly a result of water shortages. After peaking at 140 million tons in 1997, the harvest dropped in four of the following eight years, falling to an estimated 127 million tons in 2005. Only corn, China’s third major grain, has thus far avoided a decline. This is because corn prices are favorable and because the crop is not as irrigation-dependent as wheat and rice are.

Overall, China’s grain production has fallen from its historical peak of 392 million tons in 1998 to an estimated 358 million tons in 2005. For perspective, this drop of 34 million tons exceeds the annual Canadian wheat harvest. China largely covered the drop-off in production by drawing down its once vast stocks until 2004, at which point it imported 7 million tons of grain.

A World Bank study indicates that China is overpumping three river basins in the north—-the Hai, which flows through Beijing and Tianjin; the Yellow; and the Huai, the next river south of the Yellow. Since it takes 1,000 tons of water to produce one ton of grain, the shortfall in the Hai basin of nearly 40 billion tons of water per year (1 ton equals 1 cubic meter) means that when the aquifer is depleted, the grain harvest will drop by 40 million tons—-enough to feed 120 million Chinese.

Of the leading grain producers, only China has thus far experienced a substantial decline in production. Even with a worldwide grain crunch and climbing grain prices providing an incentive to boost production, it will be difficult for China to regain earlier grain production levels, given the loss of irrigation water.

Serious though emerging water shortages are in China, they are even more serious in India simply because the margin between actual food consumption and survival is so precarious. In a survey of India’s water situation, Fred Pearce reported in the New Scientist that the 21 million wells drilled in this global epicenter of well-drilling are lowering water tables in most of the country. In North Gujarat, the water table is falling by 6 meters (20 feet) per year.

In Tamil Nadu, a state with more than 62 million people in southern India, wells are going dry almost everywhere. According to Kuppannan Palanisami of Tamil Nadu Agricultural University, falling water tables have dried up 95 percent of the wells owned by small farmers, reducing the irrigated area in the state by half over the last decade.

As water tables fall, well drillers are using modified oil-drilling technology to reach water, going as deep as 1,000 meters in some locations. In communities where underground water sources have dried up entirely, all agriculture is rain-fed and drinking water is trucked in. Tushaar Shah, who heads the International Water Management Institute’s groundwater station in Gujarat, says of India’s water situation: “When the balloon bursts, untold anarchy will be the lot of rural India.”

At this point, the harvests of wheat and rice, India’s principal food grains, are still increasing. But within the next few years, the loss of irrigation water could override technological progress and start shrinking the harvest in some areas, as it is already doing in China.

In the United States, the USDA reports that in parts of Texas, Oklahoma, and Kansas-—three leading grain-producing states-—the underground water table has dropped by more than 30 meters (100 feet). As a result, wells have gone dry on thousands of farms in the southern Great Plains. Although this mining of underground water is taking a toll on U.S. grain production, irrigated land accounts for only one-fifth of the U.S. grain harvest, compared with close to three-fifths of the harvest in India and four-fifths in China.

Pakistan, a country with 158 million people that is growing by 3 million per year, is also mining its underground water. In the Pakistani part of the fertile Punjab plain, the drop in water tables appears to be similar to that in India. Observation wells near the twin cities of Islamabad and Rawalpindi show a fall in the water table between 1982 and 2000 that ranges from 1 to nearly 2 meters a year.

In the province of Baluchistan, water tables around the capital, Quetta, are falling by 3.5 meters per year. Richard Garstang, a water expert with the World Wildlife Fund and a participant in a study of Pakistan’s water situation, said in 2001 that “within 15 years Quetta will run out of water if the current consumption rate continues.”

The water shortage in Baluchistan is province-wide. Sardar Riaz A. Khan, former Director of Pakistan’s Arid Zone Research Institute in Quetta, reports that six basins have exhausted their groundwater supplies, leaving their irrigated lands barren. Khan expects that within 10–15 years virtually all the basins outside the canal-irrigated areas will have depleted their groundwater supplies, depriving the province of much of its grain harvest.

Future irrigation water cutbacks as a result of aquifer depletion will undoubtedly reduce Pakistan’s grain harvest. Countrywide, the harvest of wheat—-the principal food staple—-is continuing to grow, but more slowly than in the past.

Iran, a country of 70 million people, is overpumping its aquifers by an average of 5 billion tons of water per year, the water equivalent of one-third of its annual grain harvest. Under the small but agriculturally rich Chenaran Plain in northeastern Iran, the water table was falling by 2.8 meters a year in the late 1990s. New wells being drilled both for irrigation and to supply the nearby city of Mashad are responsible. Villages in eastern Iran are being abandoned as wells go dry, generating a flow of “water refugees.”

Saudi Arabia, a country of 25 million people, is as water-poor as it is oil-rich. Relying heavily on subsidies, it developed an extensive irrigated agriculture based largely on its deep fossil aquifer. After several years of using oil money to support wheat prices at five times the world market level, the government was forced to face fiscal reality and cut the subsidies. Its wheat harvest dropped from a high of 4.1 million tons in 1992 to 1.2 million tons in 2005, a drop of 71 percent.

Craig Smith writes in the New York Times, “From the air, the circular wheat fields of this arid land’s breadbasket look like forest green poker chips strewn across the brown desert. But they are outnumbered by the ghostly silhouettes of fields left to fade back into the sand, places where the kingdom’s gamble on agriculture has sucked precious aquifers dry.” Some Saudi farmers are now pumping water from wells that are 4,000 feet deep, nearly four-fifths of a mile (1 mile equals 1.61 kilometers).

Countries Overpumping Aquifers in 2005

Country

Population

(million)

China

1,316

India

1,103

Iran

70

Israel

7

Jordan

6

Mexico

107

Morocco

31

Pakistan

158

Saudi Arabia

25

South Korea

48

Spain

43

Syria

19

Tunisia

10

United States

298

Yemen

21

Total

3,262

A 1984 Saudi national survey reported fossil water reserves at 462 billion tons. Half of that, Smith reports, has probably disappeared by now. This suggests that irrigated agriculture could last for another decade or so and then will largely vanish, limited to the small area that can be irrigated with water from the shallow aquifers that are replenished by the kingdom’s sparse rainfall. It is a classic example of an overshoot-and-collapse food economy.

In neighboring Yemen, a nation of 21 million, the water table under most of the country is falling by roughly 2 meters a year as water use outstrips the sustainable yield of aquifers. In western Yemen’s Sana’a Basin, the estimated annual water extraction of 224 million tons exceeds the annual recharge of 42 million tons by a factor of five, dropping the water table 6 meters per year. World Bank projections indicate the Sana’a Basin-—site of the national capital, Sana’a, and home to 2 million people—-will be pumped dry by 2010.

In the search for water, the Yemeni government has drilled test wells in the basin that are 2 kilometers (1.2 miles) deep-—depths normally associated with the oil industry—-but they have failed to find water. Yemen must soon decide whether to bring water to Sana’a, possibly by pipeline from coastal desalting plants, if it can afford it, or to relocate the capital. Either alternative will be costly and potentially traumatic.

With its population growing at 3 percent a year and with water tables falling everywhere, Yemen is fast becoming a hydrological basket case. Aside from the effect of overpumping on the capital, World Bank official Christopher Ward observes that “groundwater is being mined at such a rate that parts of the rural economy could disappear within a generation.”

Israel, even though a pioneer in raising irrigation water productivity, is depleting both of its principal aquifers—-the coastal aquifer and the mountain aquifer that it shares with Palestinians. Israel’s population, whose growth is fueled by both natural increase and immigration, is outgrowing its water supply. Conflicts between Israelis and Palestinians over the allocation of water in the latter area are ongoing. Because of severe water shortages, Israel has banned the irrigation of wheat.

In Mexico-—home to a population of 107 million that is projected to reach 140 million by 2050—-the demand for water is outstripping supply. Mexico City’s water problems are well known and rural areas are also suffering. For example, in the agricultural state of Guanajuato, the water table is falling by 2 meters or more a year. At the national level, 51 percent of all the water extracted from underground is from aquifers that are being overpumped.

Since the overpumping of aquifers is occurring in many countries more or less simultaneously, the depletion of aquifers and the resulting harvest cutbacks could come at roughly the same time. And the accelerating depletion of aquifers means this day may come soon, creating potentially unmanageable food scarcity.

Citation

3 Comments

Please discuss: How does aquifer depletion effect climatic patterns?
Aquifer draw-down or over-drafting and the pumping of fossil water increases the total amount of water in the hydrosphere that is subject to transpiration and evaporation thereby increasing the atmospheric accretion of water vapour and corresponding cloud cover which are the primary absorbers of infrared radiation in the earth's atmosphere. Adding water to the system has a forcing effect on the whole earth system, an accurate estimate of which hydro-geological fact is yet to be quantified.

Excellent and very informative.
To pacify skeptics I would like to be able to trace the many claims in the article to their primary sources. For example, can a citation be provided for the quote by Christopher Ward? Thanks!

A very informative article.
If I may correct a popular misconception therein: logical as it may sound, food shortages do not lead to population reduction; in fact, the opposite occurs. In all regions in the world where population is expanding dramatically, poverty is the prevailing condition of the people. But where survival is guaranteed, and the necessities of life are easily available TO ALL, then population falls rapidly to zero growth rate and below.
Note, I said available TO ALL. In the US, for example, 40% live in poverty. The US economic system drives wealth upwards. By comparison, in Australia of the 1950s and 1960s, egalitarian income policies meant that every worker could afford two cars and a home, and unemployment was well below 1%; and even then, by choice. By 1970, population growth was in reverse, not counting immigration.
The two key factors in population control are egalitarian flows of wealth, and adequate age pensions.
In central India, if parents do not have several children, there will be no surviving males to look after them in their old age. They will starve. Contrary to claims about India's wealth, national resources are increasingly being siphoned from the masses to the Mumbai elite. And in terms of water supplies, US interests like Cocoa Cola are depleting acquifers at an alarming rate, then moving on. Free trade ideologists are encourageing the export of national resources and production, which further depletes water, and food for the national population.
Under intense US pressure, Australian politicians have attacked the trade unions that kept wages high, and now 1 in 4 Australians has insufficient income to survive. To cover up the new surge in birth rate, the Howard Government introduced a baby bonus; claiming it was this that was responsible.
Meanwhile, Australian acquifers and the Murray/Darling basin, which water most food crops, are being denied to food farmers, but are available to cotton growers and to the environmental lobby which wants fresh water to flow out to sea. Evidence links the environmental lobby to the global eugenics movement, vis a vis the WWF and Conservation Foundation; both patronised by recognised eugenics advocates, the Duke of Edinborough, and his son, Prince Charles.